In chemical recovery units where black liquor is burned, deposits tend to build up in the air nozzles, which prevent the regulation or control of the air to such nozzles after a period of time. Thus it is necessary to provide scraping or cleaning devices for these nozzles, which are periodically actuated to keep these nozzles or air ports free of built-up deposits. Various arrangements have been used in the past for both cleaning and controlling the airflow to the air nozzles. Most of these have shortcomings in that they are expensive and complicated, or do not clean the nozzles sufficiently to permit accurate control or regulation of airflow thereto.